Surfactant Protein C Mutations and Interstitial Lung Disease

摘要 特发性肺纤维化(IPF)是一种进行性瘢痕间质性肺疾病(ILD)，主要影响 仍有大量未得到满足的治疗需求的老年人。而病理生理学 IPF的基础仍然不完全被理解，这是更好地发展的另一个关键障碍 IPF的治疗结果一直缺乏翻译上相关的临床前模型。基于最近的一项 范式的转变，其中对功能失调的、脆弱的、肺泡上皮的重复损伤的概念结合在一起 由于伤口愈合反应异常被认为是疾病的“驱动力”，新的机会正在出现 用于IPF的治疗发现。肺泡2型细胞(AT2)限制性表面活性蛋白中的60多个突变 C[SP-C]基因[SFTPC]，已在散发性和家族性IPF中发现，并为 了解IPF的发病机制。为了解决IPF退伍军人的未得到满足的需求，这项提议建立在 在我们之前由功绩回顾计划资助的工作的坚实基础上，该计划表征了 SP-C的生物合成最终导致两种新的自发性肺敲入小鼠模型的产生 纤维化已经出现，在AT2细胞中以等位基因和可诱导的方式表达临床SP-C突变。我们的 已公布的数据表明，临床上与IPF相关的SFTPC突变会产生异常的SP-C 功能上分离为2种AT2细胞应激表型的原蛋白亚型：由 细胞内SP-C错误折叠(“Brichos”)或继发于ProSP-C的自噬/有丝分裂功能受损 对非本地细胞器的错误处理(“非Brichos”)。在活体肺上皮细胞中表达时，两者 非Brichos突变体(SftpcI73T)和Brichos突变体(SftpcC121G)对肺和 每种都足以引起一种时间依赖的、生理上受限的外周纤维性肺表型， 阐述了在人类IPF中报告的翻译相关生物标志物。在此基础上，我们的功绩评估更新 现在将利用这些Sftpc突变小鼠来绘制IPF中的远端肺细胞群，同时还识别和 翻译分子机制，将细胞质量控制、上皮功能障碍和 IPF/ILDS的病理生理学。在三个具体目标中，我们的实验方法将是开发独特的功能 这些遗传模型与我们计划中可用的工具和试剂相结合，旨在使细胞相互作用 质量控制和综合应激反应首先确定关键的肺泡龛细胞群 体内SP-C突变诱导的起始、损伤扩大和纤维化阶段[特定目标1]。然后 有了这张功能图，我们将把Sftpc小鼠与还原模型(如AT2有机化合物)结合起来 明确内源性内质网应激在AT2功能障碍及其异常中的作用 在IPF中发现的损伤/修复途径[具体目标2]。最后，我们将评估以下因素的下游后果 AT2代谢重编程和线粒体动力学的干扰上皮细胞质量控制 将它们对AT2表型和纤维化重塑的影响与背景联系起来[具体目标3]。作为肺泡上皮 在纤维化肺部疾病的背景下，体内功能障碍还没有得到广泛的研究，这种方法提供了 全面识别调节对突变体的反应的独特机制的独特机会 通过AT2细胞的SFTPC底物，并评估促进AT2细胞之间的串扰的途径，炎症 推动实质重塑的细胞和成纤维细胞。通过了解以下因素导致上皮损伤的途径 突变的SP-C，使用这些模型确定的机制可以交叉使用，以更好地理解IPF 一般的发病机制，促进新的靶点通路的识别，并测试新的IPF疗法。

ABSTRACT Idiopathic pulmonary fibrosis (IPF) is a progressive scarring interstitial lung disease (ILD) that affects mainly older adults for which there remains a significant unmet therapeutic need. While the pathophysiologic underpinnings of IPF remain incompletely understood, an additional critical barrier to developing better therapeutic outcomes for IPF has been a dearth of translationally relevant preclinical models. Based on a recent paradigm shift wherein the concepts of repetitive injury to a dysfunctional, vulnerable, alveolar epithelium coupled with an abnormal wound healing response are postulated as disease “drivers”, new opportunities are emerging for therapeutic discovery in IPF. Over 60 mutations in the alveolar type 2 cell (AT2) restricted, Surfactant Protein C [SP-C] gene [SFTPC], have been found in sporadic and familial IPF and provide important clues for understanding IPF pathogenesis. To address the unmet need for veterans with IPF, this proposal builds upon on a strong foundation of our prior work funded by this Merit Review program characterizing the cell biology of SP-C biosynthesis that culminated in generation of two novel knock-in mouse models of spontaneous lung fibrosis already in hand which express clinical SP-C mutants in AT2 cells in an allelic and inducible fashion. Our Published Data has demonstrated that clinical, IPF-associated SFTPC mutations produce aberrant SP-C proprotein isoforms that functionally segregate into 2 AT2 cell stress phenotypes: ER stress induced by intracellular SP-C misfolding (“BRICHOS”) or impaired autophagy/mitophagy secondary to proSP-C mistrafficking to non-native organelles (“Non-BRICHOS”). When expressed in the lung epithelium in vivo, both the non-BRICHOS mutant (SftpcI73T) and the BRICHOS mutant (SftpcC121G) are extremely toxic to the lung and each is sufficient to evoke a time-dependent, physiologically restrictive peripheral fibrotic lung phenotype that elaborates translationally relevant biomarkers reported in human IPF. Building on this, our Merit Review renewal will now leverage these Sftpc mutant mice to map distal lung cell populations in IPF while also identifying and translating molecular mechanisms linking the disrupted cellular quality control, epithelial dysfunction, and pathophysiology of IPF/ILDs. In 3 specific aims, our experimental approach will be to exploit the unique features of these genetic models combined with tools and reagents available in our program designed to interogate cell quality control and integrated stress responses to first define key alveolar niche cell populations emerging during initiation, injury amplification, and fibrosis stages induced by SP-C mutations in vivo [Specific Aim 1]. Then armed with this functional map we will couple Sftpc mice with reductionist models such as AT2 organoids to define the role of endogenous endoplasmic reticulum (ER) stress in AT2 dysfunction and the aberrant injury/repair pathways found in IPF [Specific Aim 2]. Finally, we will assess the downstream consequences of disrupted epithelial cell quality control for AT2 metabolic reprogramming and mitochondrial dynamics and then contextualize their impact on AT2 phenotypes and fibrotic remodeling [Specific Aim 3]. As alveolar epithelial dysfunction has not been studied extensively in vivo in the setting of fibrotic lung diseases, this approach offers the unique opportunity to comprehensively identify unique mechanisms mediating responses to the mutant SFTPC substrate by AT2 cells, and to assess the pathways promoting crosstalk between AT2 cells, inflammatory cells and fibroblasts that drive parenchymal remodeling. By understanding the path to epithelial injury from mutant SP-C, the mechanisms identified using these models can be cross-purposed to better understand IPF pathogenesis in general, promote identification of new target pathways, and test novel IPF therapies.